The invention relates to reinforcement of elastomeric materials, especially rubber formulations.
Short fiber reinforcement in an elastomer results in increased modulus values, but lower break strengths. This is due to the poor adhesion between the fiber and the elastomer resulting in poor transfer of shear stresses between the rubber and the fiber. The poor adhesion is due to chemical and mechanical incompatibility between the fiber and the elastomer.
Chemical incompatibility arises from polar (fiber) and non-polar (elastomer) interactions. This problem can be minimized by grafting the elastomer to the fiber.
Mechanical incompatibility arises due to the large modulus differences between the fiber and the elastomer. Fibers, in general, have a very high modulus, and elastomers, comparatively, have a very low modulus. The large difference in modulus creates a weak interface between the fiber and the elastomer, and causes poor transfer of shear stresses which develop when an elastomer is compressed or stretched and rebounds. In accordance with the present invention, mechanical compatibility between an elastomer and a fiber embedded therein can be improved by creating a modulus gradient between the elastomer and the fiber.
It is an object of this invention to improve the chemical and mechanical compatibility of an elastomer and its fiber reinforcement. It is also an object of this invention to provide modulus gradients in an elastomer matrix. Other objects of the invention will be apparent from the following description and claims.